For patients with respiratory disease the symptom of breathlessness (dyspnea) is the most frequent reason for seeking medical attention. Current methods for measuring breathlessness have patients provide ratings each minute during an incremental exercise test. Such "discrete" methods have limitations: 1) as patients breathe through a mouthpiece, they must point to a number on a scale which can lead to recording errors; 2) in patients with severe impairment only a few ratings of breathlessness are obtained; and 3) information is lost about the progressive nature of breathlessness because patients are asked for ratings at arbitrary time periods rather than when actual changes in breathlessness occur. The long-term objective of this project is to develop a continuous method to measure breathlessness in patients with respiratory and/or cardiopulmonary disease. The Phase I approach will assess breathlessness during exercise using a computer system whereby patients provide spontaneous ratings that are then related to the levels of concomitant physiological variables. The aims of this feasibility study are to establish the reliability and validity of the continuous method for measuring breathlessness. Subjects will be 24 patients with chronic obstructive pulmonary disease and a control group of 24 healthy individuals matched for age and gender. PROPOSED COMMERCIAL APPLICATION: The commercial goal is to privide the areas of respiratory physiology and sports medicine with a continuous method for measuring breathlessness during exercise. The Product will be a computer software package that can be purchased by physicians, clinics and hospitals throughout the world.